Right and wrong:
- the system comes from WC3 and was forced onto Dota. There was no choice.
It doesn't balance the items and game better, but limits the item builds, what leads to easier balancing.
The system has its advantages, too.
You can't make any caster that is not meant to cast a carry.
Windrunner. She can't really be a carry, cause she uses int. Butterfly is useless on her and she needs to build mobility + high int. Her late game build also always needs one CC item (Guinsoo's normally).
There is no way you can experiment with the items and the her too much, cause nearly 50% of the items are bad for her.
AP carries in Dota? They don't exist.
Int means AA + support or tank + support late game. Some are also pure supports late game. They deal magical dmg early and can kill, but that doesn't mean they are carries in any way.
Windrunner can be built into a semi-carry role, as a lot of int heroes tend to be built, especially those in mid, or in the suicide lane. Which, to be completely honest, is more or less the role of an AP carry in LoL. You know, they get the early levels, and have a large early-mid game presence. But, when it comes to the very end of the game, the ad carry will always out DPS them if they are any good. The only difference is late game, in LoL, AP is for damage, and in DotA, int heroes are used for CC and some damage.
Plus, just to list off a few int carries, there is Obsidian Destroyer, Silencer, Skywrath mage, Krob, Necro, Tinker, Invoker, Enchantress (if she gets a good start), and Storm Spirit. Each one can effectively carry a game.
It's actually more likely to see an int hero carrying the late game in DotA, then to see an AP carry the late game in LoL.
And please, do not talk about limiting builds. If you think DotA limits your build more than LoL, then never compare the two before. (I may be wrong on you saying it limits more or not, if I am, then sorry I assumed that's what you were implying.)